Longitudinal structure function $F_L$ at low $Q^2$ and low $x$ with model for higher twist: an update

Abstract

A reanalysis of the model for the longitudinal structure function F L (x, Q 2 ) at low x and low Q 2 was undertaken, in view of the advent of the EIC. The model is based on the photon-gluon fusion mechanism suitably extrapolated to the region of low Q 2 . It includes the kinematic constraint F L ∼ Q 4 as Q 2 → 0 and higher twist contribution which vanishes as Q 2 → ∞. Revised model was critically updated and compared to the presently available data.